Modern aircraft cockpit displays, particularly those used in aircraft for flight planning and monitoring, are capable of displaying a considerable amount of information such as flight planning information, flight profile information, airport information, airway information, navigational aid information, aircraft performance information, other aircraft information, and other information useful to a crew member in conducting or monitoring a flight.
With certain displays it is possible for a crew member to interact with the display by selecting a particular item of information on the display, and to enter certain information related to flight parameters into the display. Such information may be navigational information, communications information or information directly related to the performance characteristics of the aircraft such as various critical airspeeds and the like.
Airspeeds are particularly critical when the aircraft is in relatively slow flight, for example during takeoff or landing. At these times the pilot must be especially aware of the aircraft's airspeed because of the danger of inducing a stall. Airspeed indicators are generally of two types: older round dial airspeed indicators in which the airspeed is indicated with respect to a fixed scale around the instrument, and airspeed markers, or “bugs”, and the angular orientation of the airspeed needle give some indication of low speed; and more modern vertical tape airspeed indicators in which the speed scale moves with respect to a fixed pointer in the center of the tape. Vertical tapes lack the angular presentation of round dial instruments. Consequently, airspeed bugs and low speed range indications are vital to low speed awareness. Providing airspeed bugs and low speed range indications is particularly difficult in those instances where an older aircraft is retrofitted with more modern instrumentation which includes a vertical tape airspeed indicator. Such aircraft may not, for example, have all the sensor inputs needed to provide the added airspeed bugs or low speed range indication noted above for display on a vertical tape airspeed indicator.